Proximity sensor for X-ray apparatus

An imaging system, comprising:

• a robotic arm;
• and
• a swing arm connected to the robotic arm, the swing arm comprising:
• a radiation source;
• a detector adapted to receive radiation from the radiation source;
• a protective cover;
• and
• a proximity sensor, comprising:
• an emitter electrode disposed behind the protective cover;
• a receiver electrode disposed behind the protective cover laterally with respect to the emitter electrode,
• an oscillator coupled to the emitter electrode to cause the emitter electrode to generate an electric field that passes from the emitter electrode, through the protective cover a first time, back through the protective cover a second time, and is received by the receiver electrode, and
• an electrically driven guard electrode disposed behind the protective cover laterally between the emitter and receiver electrodes so as to prevent shortened lines of the electric field from the emitter electrode from reaching the receiver electrode,
• wherein detection of an object in proximity to the proximity sensor is indicated by a reduction of sensor output voltage from the receiver electrode;
• motive means for moving said swing arm to a desired position relative to a subject to be imaged;
• and
• means for controlling said motive means according to the output of said proximity sensor.